New HT1 owner-non runner!

Discussion - HT-1 amplifiers
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Jake_e_lee
Posts: 1
Joined: Sat Jun 15, 2019 11:39 pm

Fri Jun 21, 2019 6:43 am

Hi,I was given a non working ht1 combo by a friend.
He had been using it and it died and he says to me keep it because it was resigned to the bin!
Myself,never one to shy from a challenge,I brought it home and plugged it in.
so,the power led came on but no sound.no sound in speaker,phones or the mp3 jack.
A few tests reveal the pcb fuse gone so,i fix it with some light fuse wire.
Now...we have sound.
Plays fine for 2 minutes on clean then it distorts and the sound diminishes until nothing so I turn it off.
5 mins later...It goes again and I keep an eye on the valves and notice the 12au7 valve red plating and arcing and the 12ax7 is microphonic with the tap test.
I suspect,he kept using it with bad valves until the pcb fuse cried enough and blew.
I have 2 new valves coming for this and hopefully these cure it.
Any thoughts?
I was also instructed,there is supposedly a flaw in the pcb design where the resistors in d87 and d93 on the pcb are wrong and was advised swap these out for a 4k7 resistor and a 680 resistor which i have already done.
Hopefully..these new valves come and no more issues and i can use this ht1.
If it works out,next plan is to install a port so I can use a footswitch to change channel
Does it sound like a bad valve issue that killed the amp with the previous owner being unaware and using it until his fuse went?
Thanks in advance

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